KANSAS CITY, Mo. -- When Kansas City Chiefs coach Andy Reid sensed two years ago that he would soon need a new offensive coordinator, he called Eric Bieniemy in for a chat.

Bieniemy, at the time a veteran running backs coach already on the Chiefs' staff, was well-versed in the ground game but needed more exposure to the passing part of things. Reid told him he would need to expand this part of his coaching game if Bieniemy wanted to eventually become a coordinator and put his career on a track to someday become a head coach.

"The one thing on working with Coach Reid is you have to learn to be flexible," Bieniemy said. "He's very innovative, and he'll expand your mind. He'll push it to certain limits and then you think you're at a point and he'll push it to more."

Bieniemy took Reid's advice, and it paid off. The Chiefs promoted Bieniemy to offensive coordinator last year when former offensive coordinator Matt Nagy left to become head coach of the Chicago Bears. And this season the Chiefs led the NFL in scoring, won the AFC West title, earned their first home playoff win in 25 years and will host the New England Patriots in Sunday's AFC Championship Game at Arrowhead Stadium.

It has raised the profile of Bieniemy, who interviewed for head-coaching openings during the Chiefs' bye week. He appears destined to be the next branch of Reid's coaching tree, which is one of the most productive in football.

Before Matt Nagy took over in Chicago, he learned under Andy Reid in Kansas City. Robin Alam/Icon Sportswire

Reid's former assistants have combined for a regular-season record winning percentage of .512, which is better than that of other 2018 coaches who have had at least four former assistants move on to become head coaches. That list includes Jon Gruden, Marvin Lewis, John Harbaugh and the man he'll be standing across the field from on Sunday, Bill Belichick.

Of Belichick's many disciples, only Bill O'Brien (Texans) and Matt Patricia (Lions) were NFL head coaches this season, and only O'Brien coached a team into the playoffs -- though Nick Saban made yet another appearance in the college football national title game at Alabama.

Reid had seven former assistants working as head coaches this season: Nagy, Doug Pederson (Eagles), John Harbaugh (Ravens), Sean McDermott (Bills), Pat Shurmur (Giants), Ron Rivera (Panthers) and Todd Bowles (Jets). Harbaugh and Pederson have won Super Bowls as head coaches. Nagy, Pederson and Harbaugh coached playoff teams this season.

To Bieniemy and others, this isn't coincidence.

"One of the most important things in any profession ... is where you start," said Harbaugh, an assistant coach for Reid for nine seasons with the Philadelphia Eagles before he joined the Ravens in 2008. "Who you start with really makes a big difference. If you start with people that do it the right way -- good people, teach you the right things -- it just gives you a chance, gives you a leg up. And Andy, for me, was a big part of that in every way. I learned a great many things from him, and watching his tape now, I still learn a great many things from him.

"You get a chance to learn so much from watching him work and being around him every day. He's got a unique style. He doesn't try to be anything or do anything that's not perfectly tuned to who he is and what he believes and that kind of thing. ... You learn good things from him, [and] he's not afraid to share them with you, why he does things or how he does things and what his thinking is."

Joe Banner, the Eagles' president who hired Reid as head coach in 1999, said the most impressive thing about Reid in the interview process, and one of reasons he got the job, was the meticulous list of prospective assistant coaches he wanted to hire for Eagles staff.

"He had a list of all of these coaches he had met and notes about them and even ordered them, like it was a draft board," Banner said. "That tells you how much he appreciates surrounding himself with good people. He was looking for the best people as opposed to some coaches out there who are conscious of hiring people who aren't threats.

"Andy realizes he can't be successful unless he's surrounded by people that actually make you better. He also realizes the better he makes those people, the better he is. Investing in the time it took to properly evaluate coaches and in trying to develop them were something he prioritized. When you do that and teach as well as he does, you're going to have a lot of good coaches working for you."

"He's very innovative, and he'll expand your mind. He'll push it to certain limits and then you think you're at a point and he'll push it to more."
Eric Bieniemy

Brad Childress coached for Reid with the Eagles for seven seasons before becoming head coach of the Minnesota Vikings in 2006. He went 39-35 and took the Vikings to the NFC Championship Game in January 2010; they lost in overtime to the New Orleans Saints.

He later rejoined Reid as an assistant coach with the Chiefs before leaving at the end of last season. Childress recalled many nights as Reid's assistant sleeping in the office after hours of preparing game plans and talking football.

"But I can tell you that most of the time when I was driving in in the morning, his car was already there and a lot of times when I was leaving, his car was still there," Childress said.

"He instills that work ethic in you, and there aren't many situations you're in that he hasn't covered with you. That helps in becoming a head coach and being successful when you get the job."

To Reid, there's nothing magical about this.

"You just let them do their jobs," he said. "In a leadership position, you try to set up a format of things you want done within that but don't take away the ability of someone to let their personality show. Let them be who you've hired and have their input."

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His coaches evidently like working for him. The stability of Reid's staff in six seasons with the Chiefs is remarkable.

All but six of the main coaches from Reid's original staff remain with the Chiefs. Of the six, three (including Pederson and Nagy) left for promotions with other teams and two retired from coaching.

"He's going to hold you accountable, but he's going to let you coach," defensive coordinator Bob Sutton said. "We have certain parameters and all of that stuff, but in the end you're in charge of your area and your position. You feel like he trusts you, he wants you to be good at it. Then you have to produce that for him."

Reid was once an assistant coach himself, for 10 years in college and then seven years in the NFL. Mike Holmgren gave Reid his first NFL job in 1992 with the Green Bay Packers. The two had worked together as assistants at BYU in 1982, and, though that time together was brief, Holmgren said it made an impression on him.

"I was really observant when we first started working together of how smart he was, how he related to players, how he approached work and of his personality as a teacher," Holmgren said. "I kind of filed it away that if I ever had a chance to be a head coach, Andy would be someone I reached out to.

"When I got the job with the Packers, he was the first guy I phoned. As an assistant coach for me, he was all the things I thought he was going to be."

Reid started coaching the offensive line and tight ends with the Packers. Holmgren later made what seemed to be a radical move, moving Reid to coach the quarterbacks, including eventual Hall of Famer Brett Favre.

"He did things as an assistant the way I did them with coach [Bill] Walsh," Holmgren said. "If nothing else, I was a good student. I wrote everything down. I made lists. I made lists of things I really liked. That helps in creating your own philosophy. Andy did the same thing with me. He wrote down stuff and liked some of it and then he sprinkled in his own stuff.

"That's the way his assistants are with him, too. The guys that are coming from his staff and are head coaches on their own, you can see they were good students of Andy Reid and how he does things. It's the formula. They're bright people. They're hard-working guys. They listened to their mentor. They're implementing some of the stuff they learned from him."